The after-treatment of exhaust gas from internal combustion engines may require the use of filters and catalysts supported on high-surface area substrates. In the case of diesel engines and some gasoline direct injection engines, a catalyzed filter for the removal of carbon soot particles may be used. The filters and catalyst supports in these applications should be refractory, thermal shock resistant, stable under a range of pO2 conditions, non-reactive with the catalyst system, and should offer minimal resistance to the exhaust gas flow. Porous ceramic flow-through honeycomb substrates and wall-flow honeycomb filters may, for example, be used in these applications.